Several devices are known and in use today for performing surgery in small or difficultly accessible parts of the body, such as within the eye. In particular, various operations for the treatment of cataracts or glaucoma or vitrealretinal disorders require specialized apparatus to permit entry into the small volume of the eye and the removal therefrom of the pathologic tissue.
Conventional methods of ophthalmic surgery include the traditional technique of manual removal of the lens, the use of intraocular scissors to cut membranes, intracapsular cataract extraction with a cryoprobe, extracapsular cataract extraction, and phaco-emulsification.
Phaco-emulsification, or the so-called Kelman technique, involves the production of ultrasonic vibration of a hand-held probe, generally a titanium needle, contacting the lens or cataract. Suction means is provided through the needle for the removal of the cataract debris, and fluid flushing means is provided adjacent the needle for the inflow of artificial aqueous into the eye to prevent collapse of the eye and to cool the vibrating needle and the area in contact with it.
This method suffers from a number of disadvantages. First, the nucleus may fragment, causing corneal damage, or the nucleus may be too hard to emulsify. Second, rupture of the posterior capsule can occur easily with ultrasonic devices. Third, a great deal of manual dexterity and skill on the part of the surgeon is required to properly perform the operation. Fourth, a large amount of irrigation, or fluid exchange, is required in the anterior segment, greatly increasing the chance of corneal damage. And fifth, the likelihood of iris injury is high.
Intraocular photo-coagulation can be accomplished by means of an ophthalmic argon laser system, such as the Britt Model 152, manufactured and marketed by Britt Corporation, Los Angeles, Calif., U.S.A. This system utilizes an argon laser to deliver energy in the form of very high power via a probe including, for example, a fiber optic or quartz fiber needle to irradiate the target area of the eye.
Yet another photo-coagulation method is the Xenon Arc method which also utilizes light energy to perform ophthalmic surgery via a fiber optic delivery system. In conventional Xenon Arc systems, a great deal of light is reflected into the surgeon's eyes.
The argon laser and Xenon Arc methods suffer from additional disadvantages. Both require the presence of large lasers in the operating room which is both inconvenient and very costly, thus limiting the availability of these techniques to wealthy hospital facilities. Furthermore, while they deliver satisfactory coagulation burns to the retina, both require a pigmented tissue to be present for the absorption of their energy, and that the retinal tissue be flat against the pigmented epithelium. Finally, one cannot utilize these devices to perform photo-transections, i.e., to make incisions, or photo-cauterizations, i.e., to seal bleeding vessels, procedures which it is often desired to perform during ophthalmic surgery.
Additionally, at present, there are a number of techniques utilizing carbon dioxide lasers to perform ophthalmic surgery. These methods are, for the most part, experimental and require the presence in the operating room of a large carbon dioxide laser coupled by a delivery system including an articulating arm to a probe. One such laser system on the market today is the Sharplan laser manufactured in Israel. This system has the advantage that the carbon dioxide laser is operative on any tissue and does not require the presence of pigmented tissue. However, these probes require physical contact with the target site for coagulation, which often results in mechanical disruption of the tissue. Furthermore, the articulating arm delivery system makes surgery somewhat difficult.
It will be appreciated that all of these photo-coagulation techniques are thermal techniques. Since they require physical contact of the probe with the tissue to be operated upon, a great deal of energy is required to perform the desired operation, due to the heat sink effect of the probe itself. For example, present day carbon dioxide lasers operate at 4 watts.